Hybrid vehicles denote so-called micro hybrid vehicles, mild hybrid vehicles and full hybrid vehicles. Encompassed in particular are land-bound motor vehicles which are equipped with at least an internal combustion engine, i.e., an Otto engine, and/or a Diesel engine. Furthermore, such hybrid vehicles also have an electric motor.
Examples of vehicles already on the market are the BMW 1 series as a representative of a micro hybrid vehicle, the Honda Civic, as a representative of a mild hybrid vehicle, and the Toyota Prius, as a representative of a full hybrid vehicle. Other manufacturers also offer comparable hybrid vehicles.
While a micro hybrid vehicle merely features an automatic start-stop function and a function for recuperating the braking energy in order to charge a starter battery, and an electric machine is not used for driving the vehicle, in the case of a mild hybrid vehicle, an electric machine, i.e., a device which is able to be used both as generator and as motor, supports the internal combustion engine so as to increase the performance or to increase the efficiency. The performance increase is also referred to as “boosting”.
As is also the case in a micro hybrid vehicle, the regeneration of braking energy, i.e., the recuperation, is able to be realized in a mild hybrid vehicle as well.
In contrast to the previously briefly explained hybrid versions, in a full hybrid vehicle, the vehicle is driven directly by the output of the electric machine.
As in any other vehicle, it may happen that a defect of a vehicle assembly, such as clutches, gears, brake devices or other mechanical or electromechanical elements, for example, arises during the operation of hybrid vehicles. Conventionally, to enable the vehicle driver to at least move the vehicle out of a danger zone such as an intersection or the highway, and/or to reach a service facility in the event of such a defect, emergency running functions are initiated through substitute measures.
German Patent Application No. DE 103 16422 A1, for example, suggests a control strategy for hybrid vehicles. Also described therein is the connection of an electric motor to an internal combustion engine, the intention being that the connection takes place without jerking.
For it must be noted that the triggering or initiation of substitute measures disadvantageously causes a torque discontinuity at the drive wheels in most cases. If the emergency running function is induced by the substitute measures in a situation in which the vehicle is in a state that is critical from the aspect of vehicle dynamics to begin with, this will endanger the vehicle because, for example, the vehicle can then break away during cornering or on a slippery roadway and thereby endanger the vehicle passengers and third parties.